A collet is a device having two or more “jaws” between which an object such as a tool or a workpiece can be positioned, the jaws forming a collar around the object. The jaws of the collet are configured to constrict around the object and exert a clamping force. In one type of collet, constriction of the jaws may be effected by pushing a suitable mechanism around the circumference of the collet. In another type of collet called a draw-in collet, the collet is tapered and drawn into a sleeve to cause the jaws to constrict around the tool or workpiece. Collets are typically fabricated from steel, which allows the jaws to be sufficiently flexible relative to each other to facilitate the constriction of the tool or workpiece.
With regard to either type, the collet is held in a clamping device, which is connected to a shaft that can be rotated, which in turn causes the tool or the workpiece to rotate. In instances in which a tool is clamped in the collet and rotated, the tool is made to engage or be engaged by a workpiece. In instances in which the workpiece is clamped in the collet and rotated, the workpiece engages or is engaged by a tool.
The rotational accuracy of the tool or the workpiece affects the process of removing swarf from the workpiece. In particular, the rotational accuracy of the tool or the workpiece is typically a function of concentricity along the axis of rotation. Once clamped into a machine tool such as a lathe or a grinding machine, the tool or workpiece is adjusted to attain concentricity upon rotation. The concentricity achieved with mechanical clamping is often inadequate or compromised during rotation, thereby resulting in runout, which will detrimentally affect the finished workpiece. Concentricity is often adjusted numerous times during an operation of a machine tool.